.loader span {
  animation: loader 1.6s linear infinite;
}
@keyframes loader {
  0% {
    box-shadow: 0 0 0 rgba(0, 0, 0, 0.5);
    opacity: 0;
    transform: translateX(-50px) scale(1);
  }
  50% {
    /* 上下阴影 左右阴影 阴影模糊(可选) 阴影面积(可选) 阴影颜色(可选)  */
    box-shadow: 0 10px 50px rgba(0, 0, 0, 0.5);
    opacity: 1;
    transform: translateX(0) scale(1.2);
  }
  100% {
    box-shadow: 0 0 0 rgba(0, 0, 0, 0.5);
    opacity: 0;
    transform: translateX(50px) scale(1);
  }
}
.loader span:nth-child(1) {
  animation-delay: 0s;
}
.loader span:nth-child(2) {
  animation-delay: 0.2s;
}
.loader span:nth-child(3) {
  animation-delay: 0.4s;
}
.loader span:nth-child(4) {
  animation-delay: 0.6s;
}
.loader span:nth-child(5) {
  animation-delay: 0.8s;
}
.loader span:nth-child(6) {
  animation-delay: 1s;
}
.loader span:nth-child(7) {
  animation-delay: 1.2s;
}
